1 //===--- X86.cpp - X86 Helpers for Tools ------------------------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "X86.h"
10 #include "ToolChains/CommonArgs.h"
11 #include "clang/Driver/Driver.h"
12 #include "clang/Driver/DriverDiagnostic.h"
13 #include "clang/Driver/Options.h"
14 #include "llvm/ADT/StringExtras.h"
15 #include "llvm/ADT/StringMap.h"
16 #include "llvm/ADT/StringSwitch.h"
17 #include "llvm/Option/ArgList.h"
18 #include "llvm/Support/Host.h"
19 
20 using namespace clang::driver;
21 using namespace clang::driver::tools;
22 using namespace clang;
23 using namespace llvm::opt;
24 
getX86TargetCPU(const Driver & D,const ArgList & Args,const llvm::Triple & Triple)25 std::string x86::getX86TargetCPU(const Driver &D, const ArgList &Args,
26                                  const llvm::Triple &Triple) {
27   if (const Arg *A = Args.getLastArg(clang::driver::options::OPT_march_EQ)) {
28     StringRef CPU = A->getValue();
29     if (CPU != "native")
30       return std::string(CPU);
31 
32     // FIXME: Reject attempts to use -march=native unless the target matches
33     // the host.
34     //
35     // FIXME: We should also incorporate the detected target features for use
36     // with -native.
37     CPU = llvm::sys::getHostCPUName();
38     if (!CPU.empty() && CPU != "generic")
39       return std::string(CPU);
40   }
41 
42   if (const Arg *A = Args.getLastArg(options::OPT__SLASH_arch)) {
43     // Mapping built by looking at lib/Basic's X86TargetInfo::initFeatureMap().
44     // The keys are case-sensitive; this matches link.exe.
45     // 32-bit and 64-bit /arch: flags.
46     llvm::StringMap<StringRef> ArchMap({
47         {"AVX", "sandybridge"},
48         {"AVX2", "haswell"},
49         {"AVX512F", "knl"},
50         {"AVX512", "skylake-avx512"},
51     });
52     if (Triple.getArch() == llvm::Triple::x86) {
53       // 32-bit-only /arch: flags.
54       ArchMap.insert({
55           {"IA32", "i386"},
56           {"SSE", "pentium3"},
57           {"SSE2", "pentium4"},
58       });
59     }
60     StringRef CPU = ArchMap.lookup(A->getValue());
61     if (CPU.empty()) {
62       std::vector<StringRef> ValidArchs{ArchMap.keys().begin(),
63                                         ArchMap.keys().end()};
64       sort(ValidArchs);
65       D.Diag(diag::warn_drv_invalid_arch_name_with_suggestion)
66           << A->getValue() << (Triple.getArch() == llvm::Triple::x86)
67           << join(ValidArchs, ", ");
68     }
69     return std::string(CPU);
70   }
71 
72   // Select the default CPU if none was given (or detection failed).
73 
74   if (!Triple.isX86())
75     return ""; // This routine is only handling x86 targets.
76 
77   bool Is64Bit = Triple.getArch() == llvm::Triple::x86_64;
78 
79   // FIXME: Need target hooks.
80   if (Triple.isOSDarwin()) {
81     if (Triple.getArchName() == "x86_64h")
82       return "core-avx2";
83     // macosx10.12 drops support for all pre-Penryn Macs.
84     // Simulators can still run on 10.11 though, like Xcode.
85     if (Triple.isMacOSX() && !Triple.isOSVersionLT(10, 12))
86       return "penryn";
87 
88     if (Triple.isDriverKit())
89       return "nehalem";
90 
91     // The oldest x86_64 Macs have core2/Merom; the oldest x86 Macs have Yonah.
92     return Is64Bit ? "core2" : "yonah";
93   }
94 
95   // Set up default CPU name for PS4/PS5 compilers.
96   if (Triple.isPS4())
97     return "btver2";
98   if (Triple.isPS5())
99     return "znver2";
100 
101   // On Android use targets compatible with gcc
102   if (Triple.isAndroid())
103     return Is64Bit ? "x86-64" : "i686";
104 
105   // Everything else goes to x86-64 in 64-bit mode.
106   if (Is64Bit)
107     return "x86-64";
108 
109   switch (Triple.getOS()) {
110   case llvm::Triple::NetBSD:
111     return "i486";
112   case llvm::Triple::Haiku:
113   case llvm::Triple::OpenBSD:
114     return "i586";
115   case llvm::Triple::FreeBSD:
116     return "i686";
117   default:
118     // Fallback to p4.
119     return "pentium4";
120   }
121 }
122 
getX86TargetFeatures(const Driver & D,const llvm::Triple & Triple,const ArgList & Args,std::vector<StringRef> & Features)123 void x86::getX86TargetFeatures(const Driver &D, const llvm::Triple &Triple,
124                                const ArgList &Args,
125                                std::vector<StringRef> &Features) {
126   // If -march=native, autodetect the feature list.
127   if (const Arg *A = Args.getLastArg(clang::driver::options::OPT_march_EQ)) {
128     if (StringRef(A->getValue()) == "native") {
129       llvm::StringMap<bool> HostFeatures;
130       if (llvm::sys::getHostCPUFeatures(HostFeatures))
131         for (auto &F : HostFeatures)
132           Features.push_back(
133               Args.MakeArgString((F.second ? "+" : "-") + F.first()));
134     }
135   }
136 
137   if (Triple.getArchName() == "x86_64h") {
138     // x86_64h implies quite a few of the more modern subtarget features
139     // for Haswell class CPUs, but not all of them. Opt-out of a few.
140     Features.push_back("-rdrnd");
141     Features.push_back("-aes");
142     Features.push_back("-pclmul");
143     Features.push_back("-rtm");
144     Features.push_back("-fsgsbase");
145   }
146 
147   const llvm::Triple::ArchType ArchType = Triple.getArch();
148   // Add features to be compatible with gcc for Android.
149   if (Triple.isAndroid()) {
150     if (ArchType == llvm::Triple::x86_64) {
151       Features.push_back("+sse4.2");
152       Features.push_back("+popcnt");
153       Features.push_back("+cx16");
154     } else
155       Features.push_back("+ssse3");
156   }
157 
158   // Translate the high level `-mretpoline` flag to the specific target feature
159   // flags. We also detect if the user asked for retpoline external thunks but
160   // failed to ask for retpolines themselves (through any of the different
161   // flags). This is a bit hacky but keeps existing usages working. We should
162   // consider deprecating this and instead warn if the user requests external
163   // retpoline thunks and *doesn't* request some form of retpolines.
164   auto SpectreOpt = clang::driver::options::ID::OPT_INVALID;
165   if (Args.hasArgNoClaim(options::OPT_mretpoline, options::OPT_mno_retpoline,
166                          options::OPT_mspeculative_load_hardening,
167                          options::OPT_mno_speculative_load_hardening)) {
168     if (Args.hasFlag(options::OPT_mretpoline, options::OPT_mno_retpoline,
169                      false)) {
170       Features.push_back("+retpoline-indirect-calls");
171       Features.push_back("+retpoline-indirect-branches");
172       SpectreOpt = options::OPT_mretpoline;
173     } else if (Args.hasFlag(options::OPT_mspeculative_load_hardening,
174                             options::OPT_mno_speculative_load_hardening,
175                             false)) {
176       // On x86, speculative load hardening relies on at least using retpolines
177       // for indirect calls.
178       Features.push_back("+retpoline-indirect-calls");
179       SpectreOpt = options::OPT_mspeculative_load_hardening;
180     }
181   } else if (Args.hasFlag(options::OPT_mretpoline_external_thunk,
182                           options::OPT_mno_retpoline_external_thunk, false)) {
183     // FIXME: Add a warning about failing to specify `-mretpoline` and
184     // eventually switch to an error here.
185     Features.push_back("+retpoline-indirect-calls");
186     Features.push_back("+retpoline-indirect-branches");
187     SpectreOpt = options::OPT_mretpoline_external_thunk;
188   }
189 
190   auto LVIOpt = clang::driver::options::ID::OPT_INVALID;
191   if (Args.hasFlag(options::OPT_mlvi_hardening, options::OPT_mno_lvi_hardening,
192                    false)) {
193     Features.push_back("+lvi-load-hardening");
194     Features.push_back("+lvi-cfi"); // load hardening implies CFI protection
195     LVIOpt = options::OPT_mlvi_hardening;
196   } else if (Args.hasFlag(options::OPT_mlvi_cfi, options::OPT_mno_lvi_cfi,
197                           false)) {
198     Features.push_back("+lvi-cfi");
199     LVIOpt = options::OPT_mlvi_cfi;
200   }
201 
202   if (Args.hasFlag(options::OPT_m_seses, options::OPT_mno_seses, false)) {
203     if (LVIOpt == options::OPT_mlvi_hardening)
204       D.Diag(diag::err_drv_argument_not_allowed_with)
205           << D.getOpts().getOptionName(options::OPT_mlvi_hardening)
206           << D.getOpts().getOptionName(options::OPT_m_seses);
207 
208     if (SpectreOpt != clang::driver::options::ID::OPT_INVALID)
209       D.Diag(diag::err_drv_argument_not_allowed_with)
210           << D.getOpts().getOptionName(SpectreOpt)
211           << D.getOpts().getOptionName(options::OPT_m_seses);
212 
213     Features.push_back("+seses");
214     if (!Args.hasArg(options::OPT_mno_lvi_cfi)) {
215       Features.push_back("+lvi-cfi");
216       LVIOpt = options::OPT_mlvi_cfi;
217     }
218   }
219 
220   if (SpectreOpt != clang::driver::options::ID::OPT_INVALID &&
221       LVIOpt != clang::driver::options::ID::OPT_INVALID) {
222     D.Diag(diag::err_drv_argument_not_allowed_with)
223         << D.getOpts().getOptionName(SpectreOpt)
224         << D.getOpts().getOptionName(LVIOpt);
225   }
226 
227   // Now add any that the user explicitly requested on the command line,
228   // which may override the defaults.
229   for (const Arg *A : Args.filtered(options::OPT_m_x86_Features_Group,
230                                     options::OPT_mgeneral_regs_only)) {
231     StringRef Name = A->getOption().getName();
232     A->claim();
233 
234     // Skip over "-m".
235     assert(Name.startswith("m") && "Invalid feature name.");
236     Name = Name.substr(1);
237 
238     // Replace -mgeneral-regs-only with -x87, -mmx, -sse
239     if (A->getOption().getID() == options::OPT_mgeneral_regs_only) {
240       Features.insert(Features.end(), {"-x87", "-mmx", "-sse"});
241       continue;
242     }
243 
244     bool IsNegative = Name.startswith("no-");
245     if (IsNegative)
246       Name = Name.substr(3);
247     Features.push_back(Args.MakeArgString((IsNegative ? "-" : "+") + Name));
248   }
249 
250   // Enable/disable straight line speculation hardening.
251   if (Arg *A = Args.getLastArg(options::OPT_mharden_sls_EQ)) {
252     StringRef Scope = A->getValue();
253     if (Scope == "all") {
254       Features.push_back("+harden-sls-ijmp");
255       Features.push_back("+harden-sls-ret");
256     } else if (Scope == "return") {
257       Features.push_back("+harden-sls-ret");
258     } else if (Scope == "indirect-jmp") {
259       Features.push_back("+harden-sls-ijmp");
260     } else if (Scope != "none") {
261       D.Diag(diag::err_drv_unsupported_option_argument)
262           << A->getOption().getName() << Scope;
263     }
264   }
265 }
266